cartier



H. E. CARTIER Sept. 19, 1950 RECTIFIER Filed Nov. 8, 1945 INVENTOR.

Patented Sept. 19, 1950 UNITED STATES PATENL OFFICE RECTIFIER Harold E. Cartier, White Bear Lake, Minn.

Application November 8, 1945, Scrial No. 627,470

l 3 Claims.

Thls invention relates to rectiflers for changlng alternating current into direct current.

One of the objects of the invention is to provide a rectifier of the barrier layer type wherein a greater degree of eflciency can be achieved With a relatively small amount of parent metal.

Another object of the invention is to provide a rectifier including a body of parent metal wherein practically all of the outer surface of said parent metal is provided with a metallic negative coating, and wherein said body of parent metal is so shaped as to prevent the negative metallic coating from flaking off, and wherein nearly all of the parent metal is provided with a continuous active rectiiying surface or coating.

More specifically it is an object or the invention to provide a rectifier wherein the outer surface of the parent metal is free of abrupt changes in contour and is provided with a rectifying layer of metal which will not flaire oi under current stresses because of the fact that the body of parent metal. has no abrupt contour changes, sharp corners, etc.

The above and other objects and advantages of' the invention will more fully appear from the following description made in connection with the accompanying drawings, wherein like reference characters referto the same parts throughout the views. and, in Which:

Figure 1 is a plan view of a rectifier grid element made in accordance with the invention;

Figure 2 is an enlarged fragmentary and partial sectional view of an end portion of the grid element shown in Figure 1;

Figure 3 is an enlarged transverse sectional view through one of the round wires making up the grid elements of Figures 1 and 2;

Figure 4 is an enlarged transverse sectional view through a wire rectifier element having four fiat sides and rounded corners;

Figure 5 is an enlarged transverse sectional view through a rectifier element which is triangular in cross section and has rounded corners;

Figure 6 is a view partially in section of a rectifier assembly utilizing generally spherlcal rectifier units;

Figure 7 is an enlarged sectional view takeri approximately on the line 1-! of Figure 6; and

Figure 8 is a plan view of a half-wave bridge mater rectifier embodying the principles of the invention.

In Figure 1 there is shown a grld A made up of a continuous piece of wire having a plurality ci. multiple reverse bends. The main body of the gricl element A comprises a wire lll, bestshqwn in Figures 2 and 3, which is the parent metal 01 the rectifier. In the illustrated embodiment 01 the invention and for the purposes et description the wire body of parent metal I0 can be considered to be copper, although other suitable metals can be used. The usual barrier layer Il is shown immediately adjacent the parent metal body Il). Outside of the barrier layer Il is a layer I! 01 cuprous oxide and overhe layer of cuprous oxide is a layer of plating [3 of nickel Which forms the negative side of the rectifier clament.

In a rectifier of this type the plated surface completely surrounds the central wire of parent metal II) so that practically all of the outer surface of the element acts as a rectifier.

The outer surface of the round copper wire Il! or of any body of parent metal Which does not have abrupt changes in contour can be processed toprovide a rectifier unit, soma examples of which are shown in the drawing and will be found described below.

Figure 4 is a transverse sectional view through an elongated bar or wire of parent metal Il and,

if desired, it can be made up in a grid-like form such as the grid A of Figure 1. The rectifier element oi Figure 4 is provided with a barrier layer 15, a cuprous oxide layer l6 and a negative plating, such as a coat et nickel Il, in the same manner as the cylindrical wire rectifier element shown in Figures 1, 2 and 3.

Figure 5 shows a parent metal elongated mass or wire la having a barrier layer l9, a. cuprous oxide layer 20 and an outer negative metallic plating 2l.

If the rectifier elements shown in Figures 3, 4 and 5 are arranged in the form of a grid such as the grid A of Figure 1 it is a simple matter to connect the grid elements in banks of any desired number, depending upon the current desired. When a grid is made up in any desired shape, Figure 1 beingan example, it is etched in concentrated nitric acid and then emersed in a boiling distilled Water and afterward dried. The grids are then placed in a furnace at a temperature of 1020 to 1030 C. for a period of approximately five to ten minutes. This produces a.

layer of copper oxides, and the grids are then placed in a heat treating furnace at a temperature of approximately 500 to 530 C. for approximately one-half hour. They are then withdrawn from the furnace and immediately guenched in water at approximately C. After the quench ing step the active areas of the grids are reduced at a tcmperature cf approximately 40 C. in a strong alkali solution of formaldehyde. The

point beyond th termination of the outer nickel plate. The exposed copper or other parent metal is then tinned in a solder of low melting point.

A negative contact bar 24 is soldered to the hori-.

conta] bar portions A, as shown in Figure 1, said contact bar being in electrical contact with the outer layer l3 of nickel plating. A positive contact bar 25 which, as shown in Figure 1, may be U-shaped to receive the right hand ends or bends of the grid, is soldered to such bends, and is in contact with th exposed parent metal Il]. A plurality or grid elements such as the element A can then be connected in any suitable manner depending upon the desired capacity of the rectifier.

Figures 6 and 7 illustrate another form of the invention. In Figure 6 there is shown a plurality of generally spherical bodies 26 which are treated and coated or plated in the same manner as the rectifier elements of Figures 3, 4 and 5. As best illustrated in Figure 7, the spherical bodies 26 include cores 21 of parent metal, barrier layers 28, cuprous oxide layers 29, and outer layers of nickel plating .30. It will be seen in Figure 7 that a portion of the parent metal 21 is eut away to provide a concave socket 3! wherein the parent metal is exposed. A plurality of generally spherical rectifier elements are placed in a tubular casing 32 formed from a dielectric meter and the elements 26 are so arranged that the outer negative metallic plating 30 on one of the elements 26 is in contact with the parent metal 3 l with a next adjacent element 26, and th outer negative platings 30 of adjacent elements 26 are out of contact with each other. The arrangement shown in Figure 6 provides a series grouping of spherical elements and they embody the same general feature of the rectifier element shown in Figures 3, 4 and 5 in that the outer metallic negative coating is, by reason of the shape of the parent metal 3l, free of abrupt changes in contour. It is to be understood that any number of units such as shown in Figure 6 may be connected together to provide the desired rectifier capacity.

Figure 8 discloses a bridge meter to illustrate another application of the invention. The parent metal ocre is shown at 33, and the various layers such as described in the previously disclosed embodiments are also present in this form of unit.

In describing the rectifier elements as being free of abrupt changes in contour I mean that any change in surface configuration shall be free of relatively sharp corners as in the case of comparatively thin plates or strips. I have found 'through experimentation that where surface contour changes are made on relatively gentle curves as distinguished from sharp curves or sharp angles it is possible to apply a negative outer plating about the entire surface or substantially all of the entire surface and about such gentle changes in contour, and the rectifier unit will oDerate efiiciently and not break down. The oxide and negative outer layer will remain on the core of parent metal and practicall all of the surface of the rectifier element provides rectification.

With my invention it is possible to achieve a 4 much higher ratio of active surface for a. given weight of parent metal than is possible in a thin plate type rectifier. For this reason the rectifier structures will be relatively smaller in mess and for use will be less expensive in proportion to the amount of direct current drawn from them.

In connection with the elongated or wire type of rectifier element described above it should be noted that it is more easily cooled than a fiat thin plate because it has a larger surface for a given mass. By reason of the fact that electrical rectiflers are limited to a greater extent by a. minimum temperature rise factor, the greater cooling surface of a structure embodying my invention will greatly reduce the size and cost of the unit.

Through experimentation and for some reason not thoroughly understood by me, a much higher ratio of forward current to backward current can be obtained in rectifier elements constructed in accordance with the invention. Since the backward current goes directly into heat, the low backward current in an element such as disclosed results in considerable efficiency.

I have found that for a reason which is also not well understood that the rectifier disclosed herein improves with age instead of falling of! in efficiency as is the case with a thin plate type rectifier, and the rectifying units will operate relatively farther from peak capacity. This naturally will increas the effective operative life of the unit.

In a grid type rectifier such as illustrated in Figure 1 and wherein, the plated outer surface completely surrounds the parent metal there is sufficient mechanical strength to permit soldering directly to the rectifier elements with a low melting point solder. This construction produces a metallic bond directly with the plated surface, and has the advantage of eliminating the dimculties of mechanical contacts such as are commonly used in the above mentioned thin plate rectifiers.

There is another distinction between what might be termed my wire type rectifier unit and the fiat thin plate type. Assuming that rectification is due to a stressed condition set up between the oxide and the copper as the unit 15 quench6d from a high temperature, it is possible to explain the difierences in behavior of plates and wires and also the relatively large masses such as the generally spherical elements 26. If the stress is higher than the minimum creep strength of copper then the metal will move to relieve the stresses at some definite rate. This assumption is strengthened by the fact that the aging curves of the ordinary thin rectifier plates are very similar to the creep curves cf copper. In a plate the stresses can be relieved in two coordinated directions but in the wire these stresses are relieved in only one direction. For that reason it is believed that in a plate rectifier the stresses can be relieved to a lower value than in the wire type or roughly spherical type disclosed. Based on the theory that a definite quantity of stress which will produce optimum rectification, the plate type of rectifier will not reach such optimum and will begin to relieve its stresses at some point below 5 rectifier than the elongated w1re type whlch in turn is much,more stable than the fiat thln plate type.

It W111, of course, be understood that while I have referred to a rectifier of the copper oxide type, my invention 1s intended to apply to all 9.]- ternating current rectifiers of the barrier layer class, and that var1ous changes may be made in the form, details, arrangements and proportions et the units w1thout departing from the scope of my invention.

What 1 clalm 1s:

1. In an altemating current rectifler of the barrler layer type, an elongated solid wlre-like core of parent metal havlng relatively sharp bends at spaced points therealong to produce a compact structure having a considerable length of wire thereln, and said core being substantially completely covered by the barrier layer and an outer metallic coatlng except et the bends in said cote.

2. The structure in claim 1 and the ends of 6 sald w1re being free 01. sald barrier layer and outer metallic coating.

3. In an alternating current rectifier of the barrier layer type, an elongated wire-like solid core et parent metal, the outer surface of said ocre having a barrier layer thereon and an outer metallic coating, and said cors being free of said barrier layer and said outer metallc coating at a point between the ends of the core to provide an electrical contact point and to produce a. half wave rectifier.

HAROLD E. CARTIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 20 1,842,212 S1epian Jan. 19, 1932 2,189,617 Siebert et al Feb. 6.. 1940 2,406,806 Clarke Sept. 3, 1946 

